1. Technical Field of the Invention
The present invention relates to color filter substrates, methods for manufacturing color filter substrates, liquid crystal devices, and electronic apparatuses, and more particularly, relates to a transflective liquid crystal device which can improve color purity of display in a transmission mode while brightness and color purity of display in a reflection mode are not degraded and which has superior image quality.
2. Description of the Related Art
As liquid crystal devices, there have been known a transmission type liquid crystal device which performs display using light emitted from a backlight embedded therein and a reflection type liquid crystal device which performs display using outside light such as sunlight. The former liquid crystal device has an advantage in that display can be viewed in a dark place where outside light is not sufficient; however, since a backlight is always turned on, there has been a problem in that power consumption is increased. In contrast, the latter liquid crystal device can save power since lighting means is not embedded therein; however, there has been a problem in that it is difficult to view displays in a dark place.
Accordingly, as a liquid crystal device having advantages of the two devices described above, a transflective liquid crystal device has been known in which display is performed in a dark place in a transmission mode using light emitted form a backlight embedded in the device, and in a bright place with sufficient outside light, display is performed in a reflection mode using outside light. In the transflective liquid crystal device, since display can be viewed in a dark place and also in a bright place using outside light, compared to a transmission type liquid crystal device in which a backlight is always turned on, power saving can be performed.
The transflective liquid crystal device has the primary structure comprising a pair of substrates opposing each other, a liquid crystal layer provided therebetween, and transflective layers provided on a surface at the liquid crystal layer side of one of the substrates, which substrate is located at the side opposite to the viewing side. The transflective layer is formed of, for example, a reflection layer having aperture portions, such as slits, formed in respective dots, and in the transflective layer having the structure described above, the aperture portions and a region other than the aperture portions serve as light transmission portions and light reflection portion, respectively. In addition, a transflective liquid crystal device, which comprises color filters provided on one of the substrates and which is capable of performing color display, has also been known. Hereinafter, a substrate provided with color filters is referred to as xe2x80x9ccolor filter substratexe2x80x9d.
In a conventional transflective liquid crystal device, light emitted from a backlight passes through a substrate at the backlight side, a liquid crystal layer, and the substrate at an observer side in that order and is then emitted to the observer side, and by the light described above, display in a transmission mode can be performed. In addition, after passing through the substrate at the observer side and the liquid crystal layer in that order, outside light is reflected from a transflective layer provided on the substrate at the backlight side and is then emitted to the observer side, and by the light described above, display in a reflection mode can be performed.
Accordingly, in a transflective liquid crystal device capable of performing color display, when display is performed in a transmission mode, light incident on a liquid crystal panel passes through the color filter only once and is then emitted to the observer side, and on the other hand, when display is performed in a reflection mode, light incident on the liquid crystal panel passes through the color filter twice before and after being reflected from the transflective layer and is then emitted to the observer side.
As the color filter, a color filter comprising pigment dispersion color portions having red (R), green (G), and blue (B) colors has been widely used. In FIG. 20(a), examples of spectral characteristics (the relationship between wavelength of visible light (light having a wavelength of 400 to 700 nm) incident on the liquid crystal panel and transmittance thereof) of the individual color portions of the pigment dispersion color filter are shown. In FIG. 20(a), R, G, and B show examples of spectral characteristics of the red color portion, the green color portion, and the blue color portion, respectively. Since the spectral characteristics shown in FIG. 20(a) are obtained when light passes through the color filter once, the data shown in this figure corresponds to the spectral characteristics of the color filter when display is performed in a transmission mode.
As shown in FIG. 20(a), the red, green, and blue color portions forming the color filter are provided so as to primarily allow red light (light having wavelengths centered at and near 650 nm), green light (light having wavelengths centered at and near 550 nm), and blue light (light having wavelength centered at and near 450 nm) to pass therethrough, respectively; however, it is also understood that every color portion allows any light having a visible wavelength to pass therethrough. That is, light passing through each color portion of the color filter includes a part of the light having a wavelength which is not desirably displayed although the amount of said part of the light is small as compared to that of another part of the light having a wavelength which is desirably displayed. This results in lowering color purity.
In addition, since spectral characteristics in the case in which light passes"" through the color filter twice, that is, spectral characteristics of the color filter when display is performed in a reflection mode, is the square of the spectral characteristics obtained when light passes through the color filter once, for example, the above spectral characteristics are shown in FIG. 20(b).
As shown in FIGS. 20(a) and 20(b), in the conventional transflective liquid crystal device, the spectral characteristics of the color filter in a transmission mode and that of the color filter in a reflection mode are substantially different from each other, and compared to the case in which display is performed in a reflection mode, display performed in a transmission mode has a problem in that the color purity of display is low (range of color reproducibility is small).
The present invention was made in consideration of the situations described above, and an object of the present invention is to provide a color filter substrate which is to be provided in a transflective liquid crystal device, the color filter substrate being capable of improving the color purity of display in a transmission mode while the brightness and color purity of display in a reflection mode are not degraded, and is to provide a manufacturing method thereof. In addition, another object of the present invention is to provide a transflective liquid crystal device capable of improving the color purity of display in transmission mode while the brightness and color purity of display in a reflection mode are not degraded, and is to provide an electronic apparatus comprising this liquid crystal device.
Through research of the inventor of the present invention to solve the problems described above, a color filter substrate, a method for manufacturing a color filter substrate, a liquid crystal device (transflective liquid crystal device), and an electronic apparatus described below were invented.
A first color filter substrate of the present invention for forming a liquid crystal panel, comprises a base body; transflective layers provided on the base body, each having light transmission portions and light reflection portions; and color filters on the base body, each including a first color filter formed of color portions having colors different from each other and a second color filter formed of color portions having colors different from each other; wherein the first color filter is provided so that the color portions thereof correspond to the light transmission portions of the transflective layers, the second color filter is provided so that the color portions thereof correspond to the light reflection portions of the transflective layers, and the first color filter has spectral characteristics different from those of the second color filter.
A second color filter substrate of the present invention forms a liquid crystal panel which includes a counter substrate, a liquid crystal layer provided between the second color filter substrate and the counter substrate, and transflective layers provided on the counter substrate, each having light transmission portions and light reflection portions. The second color filter substrate described above comprises a base body; and color filters provided on the base body, each having a first color filter formed of color portions having colors different from each other and a second color filter formed of color portions having colors different from each other, wherein the first color filter is provided so that the color portions thereof correspond to the light transmission portions of the transflective layers, the second color filter is provided so that the color portions thereof correspond to the light reflection portions of the transflective layers, and the first color filter has spectral characteristics different from those of the second color filter.
That is, a color filter substrate, provided in a conventional transflective liquid crystal device, has the structure in which color filters for transmission mode display and color filters for reflection mode display have the same spectral characteristics; however, the color filter substrate of the present invention has the structure in which the first color filters for transmission mode display and the second color filters for reflection mode display have spectral characteristics different from each other. Accordingly, in a transflective liquid crystal device provided with the color filter substrate of the present invention, the color purity of display in a transmission mode and the color purity of display in a reflection mode can be independently adjusted.
Accordingly, a color filter substrate for use in a transflective liquid crystal device can be provided which can improve the color purity of display in a transmission mode while the brightness and color purity of display in a reflection mode are not degraded.
In the color filter substrate of the present invention, the first color filters and the second color filters may be formed on the same layer or different layers.
In addition, when display is performed in a transmission mode, light incident on the liquid crystal panel passes through the first color filter once and is then emitted to the observer side, and when display is performed in a reflection mode, light incident on the liquid crystal panel passes through the second color filter having spectral characteristics different from those of the first color filters twice and is then emitted to the observer side. Accordingly, when the spectral characteristics of the first and the second color filters are adjusted so that the color purity of the first color filter is higher than that of the second color filter of the color filter substrate according to the present invention, in a transflective liquid crystal device provided with the color filter substrate described above, the color purity of display in a transmission mode can be improved while the brightness and color purity of display in a reflection mode are not degraded.
In addition, in the color filter substrate of the present invention, the spectral characteristics of the first and the second color filters can be adjusted by compositions of the color portions or by the compositions and thicknesses thereof.
The color filter substrate of the present invention preferably has the structure in which at least one of the light transmission portions and at least one of the light reflection portions of the transflective layer be provided in each dot which forms a display region of the liquid crystal panel, and one of the color portions of the first color filter and one of the color portions of the second color filter, which are provided in the same dot, have the same color. When the color filter substrate having the structure described above is provided in a transflective liquid crystal device, display in a transmission mode or display in a reflection mode can be selectively performed in each dot by a switching operation.
In the color filter substrate of the present invention, a shading layer is preferably provided along the periphery of each dot which forms the display region of the liquid crystal panel. When the color filter substrate having the structure described above is provided in a transflective liquid crystal device, the periphery of each dot, which does not contribute toward performing display, can be shaded, and hence the contrast can be improved.
In addition, in each dot which forms the display region of the liquid crystal panel, a partition for separating the color portion of the first color filter from the color portion of the second color filter is preferably formed. In the structure described above, since the first color filters and the second color filters can be formed by an inkjet method, compared to the case in which the first color filters and the second color filters are formed by a photolithographic method, simplification of the manufacturing process and manufacturing cost saving can be significantly performed. A method for forming the color filter substrate of the present invention will be described below.
Next, a method for manufacturing the color filter substrate of the present invention will be described.
A method for manufacturing a first color filter substrate of the present invention is a method for manufacturing a color filter substrate having the structure in which at least one light transmission portion and at least one reflection portion of the transflective layer are formed in each dot which forms the display region of the liquid crystal panel, and one of the color portions of the first color filter and one of the color portions of the second color filter, which are formed in the same dot, have the same color.
The method described above comprises a step of forming the second color filters on the base body by a photolithographic method; a step of supplying droplets of coloring materials by an inkjet method to regions, which correspond to the light transmission portions of the transflective layers, of the base body provided with the second color filters; a step of annealing the supplied coloring materials for forming the first color filters.
In the case in which the color filter substrate has the shading layer provided along the periphery of each dot which forms the display region of the liquid crystal panel, the method described above may further comprise a step of forming the shading layer by a photolithographic method on the base body along the periphery of each dot which forms the display region of the liquid crystal panel.
In addition, in the case in which the color filter substrate has the shading layer formed along the periphery of each dot which forms the display region of the liquid crystal panel, instead of the step of forming the shading layer by a photolithographic method, the method described above may further comprise a step of supplying droplets of a shading material by an inkjet method to predetermined positions of the base body provided with the second color filters and a step of annealing the supplied shading material for forming the shading layer along the periphery of each dot which forms the display region of the liquid crystal panel.
A method for manufacturing a second color filter substrate of the present invention is a method for manufacturing a color filter substrate having the structure in which at least one of the light transmission portions and at least one of the reflection portions of the transflective layer are formed in each dot which forms the display region of the liquid crystal panel, one of the color portions of the first color filter and one of the color portions of the second color filter, which are formed in the same dot, have the same color, and the shading layer is provided along the periphery of each dot which forms the display region of the liquid.
The method described above comprises a step of forming the shading layers on the base body; a step of forming the first color filters by a photolithographic method on the base body; a step of supplying droplets of coloring materials to regions, which correspond to the light reflection portions of the transflective layers, of the base body provided with the shading layers and the first color filters; and a step of annealing the supplied coloring materials for forming the second color filters.
A method for manufacturing a third color filter substrate of the present invention is a method for manufacturing a color filter substrate having the structure in which at least one of the light transmission portions and at least one of the reflection portions of the transflective layer are formed in each dot which forms the display region of the liquid crystal panel, one of the color portions of the first color filter and one of the color portions of the second color filter, which are formed in the same dot, have the same color, the shading layer is provided along the periphery of each dot which forms the display region of the liquid, and the partition is provided in each dot for separating the color portion of the first color filter from that of the second color filter.
The method described above comprises a step of forming the shading layers on the base body; a step of forming the partitions on the base body; a step of supplying droplets of first coloring materials by an inkjet method to regions, which correspond to the light transmission portions of the transflective layers, of the base body provided with the shading layers and the partitions; a step of annealing the supplied first coloring materials for forming the first color filters; a step of supplying droplets of second coloring materials by an inkjet method to regions, which correspond to the light reflection portions of the transflective layers, of the base body provided with the shading layers and the partitions; and a step of annealing the supplied second coloring materials for forming the second color filters.
According to the methods for manufacturing the first to the third color filter substrates of the present invention, since at least one of the first color filter and the second color filter can be formed by an inkjet method, compared to the case in which the first color filters and the second color filters are formed by a photolithographic method, simplification of the manufacturing process and manufacturing cost saving can be performed.
When color filters are formed by a photolithographic method, after coloring materials having photosensitivity are applied to the entire surface of the base body, color filters composed of color portions having a predetermined pattern are formed by exposure and development of the coloring materials. In contrast, when the color filters are formed by an inkjet method, after droplets of coloring materials are supplied only to regions at which color portions are to be formed, color filters composed of color portions having a predetermined pattern can be formed by annealing.
Accordingly, when the color filters are formed by an inkjet method, compared to the case in which color filters are formed by a photolithographic method, the number of steps can be decreased. In addition to the decrease in the number of steps, since it becomes unnecessary to apply coloring materials to the entire surface of the base body, the usage of the coloring materials can be significantly decreased, and as a result, manufacturing cost can be decreased.
Next, a liquid crystal device of the present invention will be described.
The liquid crystal device (transflective liquid crystal device) of the present invention, in which display in a transmission mode or display in a reflection mode is selectively performed by a switching operation, comprises a liquid crystal panel; and lighting means disposed at the side opposite to a viewing side of the liquid crystal panel. In the liquid crystal device described above, the liquid crystal panel comprises a color filter substrate; a counter substrate opposing thereto; a liquid crystal layer provided between the color filter substrate and the counter substrate; transflective layers provided on one of the color filter substrate and the counter substrate, each having light transmission portions and light reflection portions; and color filters provided on the color filter substrate, each having a first color filter formed of color portions having colors different from each other and a second color filter formed of color portions having colors different from each other; wherein the first color filter is provided so that the color portions thereof correspond to the light transmission portions of the transflective layers, the second color filter is provided so that the color portions thereof correspond to the light reflection portions of the transflective layers, and the first color filter has spectral characteristics different from those of the second color filter.
In the liquid crystal device (transflective liquid crystal device) of the present invention, as is the color filter substrate of the present invention, since the first color filters for transmission mode display and the second color filters for reflection mode display are formed so as to have spectral characteristics different from each other, while the brightness and color purity of display in a reflection mode are not degraded, the color purity of display in a transmission mode can be improved, and hence the image quality can also be improved.
In the liquid crystal device (transflective liquid crystal device) of the present invention, when the spectral characteristics of the first and the second color filters are adjusted so that the color purity of the first color filter is higher than that of the second color filter, while the brightness and color purity of display in a reflection mode are not degraded, the color purity of display in a transmission mode can be improved.
In addition, in the liquid crystal device (transflective liquid crystal device) of the present invention, the spectral characteristics of each of the first and the second color filters can be adjusted by compositions of the color portions or by the compositions and thicknesses thereof.
The liquid crystal device (transflective liquid crystal device) of the present invention preferably has the structure in which at least one of the light transmission portions and at least one of the light reflection portions of the transflective layer be provided in each dot which forms the display region of the liquid crystal panel, and one of the color portions of the first color filter and one of the color portions of the second color filter, which are provided in the same dot, have the same color. When the liquid crystal device having the structure described above is formed, display in a transmission mode or display in a reflection mode can be selectively performed in each dot by a switching operation.
In the liquid crystal device (transflective liquid crystal device) of the present invention, the color filter substrate preferably has a shading layer provided along the periphery of each dot which forms the display region of the liquid crystal panel. According to the structure described above, the periphery of each dot, which does not contribute toward performing display, can be shaded, and hence the contrast can be improved.
In each dot which forms the display region of the liquid crystal panel, a partition for separating the color portion of the first color filter from the color portion of the second color filter is preferably formed. In the structure described above, since the first color filters and the second color filters can be formed by an inkjet method, compared to the case in which the first color filters and the second color filters are formed by a photolithographic method, simplification of the manufacturing process and manufacturing cost saving can be significantly performed.
In addition, in the liquid crystal device (transflective liquid crystal device), as the transflective layer described above, there may be mentioned, for example, a reflection layer provided with aperture portions, in which the aperture portions serve as the light transmission portions, and the reflection layer other than the aperture portions serves as the light reflection portion.
In addition, in the liquid crystal device (transflective liquid crystal device), as the transflective layer described above, there may be mentioned, for example, a reflection layer provided with at least one slit portion at one or two sides thereof, in which the slit portion serves as the light transmission portion, and the reflection layer other than the slit portion serves as the light reflection portion.
Furthermore, when being provided with the liquid crystal device (transflective liquid crystal device) of the present invention described above, an electronic apparatus can be provided which can improve color purity of display in transmission mode while brightness and color purity of display in reflection mode are not degraded and which has superior image quality.